I have read about different experimental studies using stem cells by in vitro assays even when furthered with in vivo xenograft assays, they use three independent experiments and published them in highly indexed journals without any query. I have carried out an in vitro study on sickle red cells, I used three repeated (independent) tests. But, like Prof. Booth wrote above, I think it depends on your research question, mainly. The best approach may be to work with a good statistician for a guide.

As always, an appropriate sample size, depends on the research question, the population to be sampled and the accuracy of estimation required. I recommend this link: https://www.google.com/search?rlz=1C1CHBF_enUS874US874&ei=i6QWXrerApq7tQauu7zQBQ&q=choice+of+sample+size+for+in+vitro+medical+studies&oq=choice+of+sample+size+for+in+vitro+medical+studies&gs_l=psy-ab.3...402543.447175..448121...2.2..3.517.9104.91j10j5-1....2..0....1..gws-wiz.....6..0i71j33i160j0i362i308i154i357j0i273j0i67j0j0i67i70i249j0i22i30j33i22i29i30j33i299.5dh0Xf279Xo&ved=0ahUKEwj3nOqB0PXmAhWaXc0KHa4dD1oQ4dUDCAs&uact=5

Best wishes, D. Booth

I have read about different experimental studies using stem cells by in vitro assays even when furthered with in vivo xenograft assays, they use three independent experiments and published them in highly indexed journals without any query. I have carried out an in vitro study on sickle red cells, I used three repeated (independent) tests. But, like Prof. Booth wrote above, I think it depends on your research question, mainly. The best approach may be to work with a good statistician for a guide.

Sneha Sunil Kothare - Thank you for your question. Usually, we measure sample size when we have a population that we aim to study. Because we cannot review the whole "population", we measure the sample size and sample power. However, when we plan to use in vitro studies, we have no population. For example, we are using isolated liver cells to test the toxicity of a chemical in vitro; such design will need a control group (experimental group vs control group). However, we have no population. The sample size here is the number of experiments we conduct on liver cells isolated from different rats (not the same rat). The important thing here is to ensure that the number of experiments is the minimal number that allows statistical significance differences when the two groups compared. I would like to leave with you this guide to see the statistical approach to calculate the sample and the effect of differences in number of experiments/animals in sample size.